Processed Food in Childhood Linked With Lower Lung Function in Adolescence

A diet high in processed food at age 7 is associated with lower lung function at age 15, whereas a health-conscious diet is associated with higher lung function, according to study findings published in Respiratory Research.

Researchers sought to determine how 3 mid-childhood dietary patterns —a health-conscious diet vs a traditional diet vs a processed food diet — affected lung function and incident asthma in adolescence, using data from the Avon Longitudinal Study of Parents and Children (ALSPAC).

The ALSPAC, a population-based birth cohort that recruited 15,454 pregnant women in Avon, UK, between April 1991 and December 1992, categorized children as having 3 principal dietary patterns — processed, traditional, and health conscious — based on parental responses to food frequency questionnaires administered when children were approximately 7 years old. The ALSPAC also recorded children’s lung function measures at age 15.5 years, including post-bronchodilator forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), and forced expiratory flow at 25%-75% of FVC (FEF_25–75).

In the current analysis, investigators examined the demographics of children within the 3 dietary categories and used multivariable adjusted analyses to calculate correlations between lung function measures and the 3 dietary categories. Children within each category were further divided into quartiles based on how strongly they fit into the particular category (as determined by questionnaire scores). The researchers also analyzed the relationship between children’s dietary categories and their likelihood of having incident asthma, defined as newly diagnosed cases of asthma in children at age 11 or 14 years.

Notably, children in the health-conscious diet category with higher questionnaire scores were more likely to have a history of food allergy, higher hours of vigorous physical exercise, to have been exclusively breastfed, to live in rural and “least deprived” areas, and to have mothers with a higher level of education who didn’t smoke. These children were more likely to consume dietary supplements and had a higher intake of vitamins A, C, D, and E, and β-carotene, zinc, selenium, fiber, and long-chain omega-3 from fish. Children in the processed diet category had these relationships in the opposite direction and they were associated with a higher body mass index at 9 years. The researchers noted that patterns of parent/child characteristics were less identifiable among children in the traditional diet category.

Investigators found modest correlations between the processed and health-conscious dietary patterns and some measures of lung function. The processed dietary pattern was negatively associated (non-linearly) with FVC (regression coefficient comparing top versus bottom quartile of pattern score [r²], -.17; 95% CI, -0.33 to -0.01; P for trend=.03) in multivariable-adjusted models, while the health-conscious dietary pattern was positively associated with FEV₁ (r², 0.16; 95% CI, 0.01-0.31; P for trend=.04) and positively associated with FVC (r², 0.18; 95% CI, 0.04-0.33; P for trend=.02). Potential mediators of adiposity, dietary fiber, vitamin D, long-chain omega-3, and antioxidants did not explain these relationships, though the relationships may depend partly on genetic make-up.

The SCGB1A1 and GPX4 gene polymorphisms modified the associations between the health-conscious and processed patterns and lung function. Investigators found no evidence of association between traditional dietary pattern and lung function, nor was there any evidence of associations between any dietary pattern and FEF_25-75 or incident asthma. Sensitivity analysis yielded the same results. Investigators found no evidence of effect modification by sex, maternal smoking, polymorphic variants of most antioxidant genes, or outdoor particulate matter up to 10 µm in size.

Among the study’s limitations are: its failure to include a sizable proportion of eligible children at 7 years; possible collider bias; misclassification of dietary exposures; a preponderance of White participants; and a lack of generalizability.

“A ‘health-conscious’ diet in mid-childhood was associated with higher subsequent lung function, while a diet high in processed food was associated with lower lung function,” investigators concluded. They wrote “We did not find evidence for an association between the ‘traditional’ pattern score and lung function, or between any dietary pattern and incident asthma.”